Build ipc_mojo_unittests in //mojo:tests and mandoline:all.

Build ipc_mojo_unittests in //mojo:tests and mandoline:all.

My recent CL added ipc_mojo_unittests to these bots:
  http://build.chromium.org/p/chromium.mojo/console
  https://codereview.chromium.org/1189133005/
They only build mandoline:all, which doesn't include the tests.

I can remove this test from those bots if we prefer.
For now, I'm adding this dependency to make the bots green.

BUG=NONE
TEST=Bots go green.
TBR=sky@chromium.org
NOTRY=TRUE

Review URL: https://codereview.chromium.org/1197533002

Cr-Commit-Position: refs/heads/master@{#335191}